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Re: kellner's ankle abstract




Nick Pharris wrote:

> Quoting David Peters <davidrpeters@earthlink.net>:
>
> > As I've always said, just look at the feet. All archosaurs tend to diminish
> > toes four and five. All crocs lose toe five. All dinos lose most of toe 
> > five.
> > Pteros and protorosaurs don't until the Late Jurassic.
>
> However, though toe V is long in basal pterosaurs, it only consists of two
> phalanges, which implies to me that it had been reduced and then re-elongated
> for whatever reason.
>
> Nick Pharris
> Ph.D. Candidate
> Department of Linguistics
> University of Michigan

Thanks, Nick.

Interesting assumption.  IMHO this is the same reasoning that Feduccia et al. 
use
when they say that there's a bird ancestor out there, we just haven't found it
yet. In other words, you might be inventing an explanation for the lateral toe
when no invention is necessary. I remember when some of the head honchos were
saying that pedal digit V was somehow genetically linked to manual digit IV and
when one elongated, the other did too.  Yes, I scratched my head at that one 
too.

Another point: phalanx reduction can come about two ways: via loss or via 
fusion.
The "loss" of one wing phalanx in Nyctosaurus comes about via fusion of 
m4.2+m4.3
for instance. M4.4 remains pretty much the same in morphology. When I mentioned
that to Greg Brown, he said, funny, he had never thought of that possibility. 
IMHO
the same thing happens in ptero feet. Two short phalanges make one long one on
digit V.

Why not go with the more parsimonious answer that the bird=dinosaur crowd is
pushing? i.e. Cladistics doesn't find ancestors exactly. Cladistics only tells 
us,
from all of the possibilities we input, which makes the best sister taxa. And
there are better matches in the protorosaurs than anywhere in the archosaurs -- 
at
present. They just haven't been input that often.

Of course you can always wait for a better archosaur. Lots of people are doing
just that.

David Peters
St. Louis